Collision-induced Dissociation Pathways Research Articles

Kendrick mass defect analysis - a tool for high-resolution Orbitrap mass spectrometry of native lignin.

Lignin is the second most abundant biopolymer in nature and a promising renewable feedstock for the production of aromatic compounds, composite materials, sorbents, etc. Being a complex mixture of oligomeric molecules with anirregular structure, natural lignin is an extremely difficult object to study. Its molecular level characterization requires advanced analytical techniques among which atmospheric pressure photoionization Orbitrap mass spectrometry holds a promising place. In the present study, Kendrick mass defect (KMD) analysis was proposed to facilitate the visualization and interpretation of Orbitrap mass spectra of the biopolymer on an example of Siberian pine dioxane lignin preparation. The use of the typical guaiacylpropane structure C10H12O4 as a Kendrick base unit made it possible to effectively identify oligomer series with different polymerization degrees and structurally related compounds, as well as to reliably determine the elemental compositions and structures of oligomers with high molecular weights (> 1kDa). For the first time, KMD analysis was applied to the interpretation of the complex tandem mass spectra of lignin oligomers, rapid discrimination of the product ion series, and the establishment of the main collision-induced dissociation pathways. It was demonstrated that especially promising was the use of KMD filtering in the study of broadband fragmentation tandem mass spectra, which allows for the structural characterization of all oligomers with a particular degree of polymerization.

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels-Alder reaction with inverse electron demand.

The mechanism of an L-proline-catalyzed pyridazine formation from acetone and aryl-substituted tetrazines via a Diels–Alder reaction with inverse electron demand has been studied with NMR and with electrospray ionization mass spectrometry. A catalytic cycle with three intermediates has been proposed. An enamine derived from L-proline and acetone acts as an electron-rich dienophile in a [4 + 2] cycloaddition with the electron-poor tetrazine forming a tetraazabicyclo[2.2.2]octadiene derivative which then eliminates N2 in a retro-Diels–Alder reaction to yield a 4,5-dihydropyridazine species. The reaction was studied in three variants: unmodified, with a charge-tagged substrate, and with a charge-tagged proline catalyst. The charge-tagging technique strongly increases the ESI response of the respective species and therefore enables to capture otherwise undetected reaction components. With the first two reaction variants, only small intensities of intermediates were found, but the temporal progress of reactants and products could be monitored very well. In experiments with the charge-tagged L-proline-derived catalyst, all three intermediates of the proposed catalytic cycle were detected and characterized by collision-induced dissociation (CID) experiments. Some of the CID pathways of intermediates mimic single steps of the proposed catalytic cycle in the gas phase. Thus, the charge-tagged catalyst proved one more time its superior effectiveness for the detection and study of reactive intermediates at low concentrations.

Collision-induced dissociation pathways of H1-antihistamines by electrospray ionization quadrupole time-of-flight mass spectrometry.

Over the past decades, mass spectrometry technologies have been developed to obtain mass accuracies of one ppm or less. Of the newly developed technologies, quadrupole time-of-flight mass spectrometry (Q-TOF-MS) has emerged as being well suited to routine and high-throughput analyses of pharmaceuticals. Dietary supplements and functional foods have frequently been found to be contaminated with pharmaceuticals. In our continuous efforts to develop methodologies to protect public health against adulterated dietary supplements, we have constructed a mass spectral database for 21 H1-antihistamines encountered as adulterants by using liquid chromatography-electrospray ionization (LC-ESI)/Q-TOF-MS, and have proposed their possible collision-induced dissociation pathways. This database will be very useful for the rapid and accurate detection of H1-antihistamines (known) and their analogues (unknown) illegally added to dietary supplements as well as in other sample matrices.

Collision-induced dissociation pathways of protonated Gly2NH2 and Gly3NH2 in the short time-scale limit by chemical dynamics and ion spectroscopy

In this work we have studied the collision induced dissociation (CID) of C-terminally amidated, protonated di- and tri-glycine by means of chemical dynamics simulations from on-the-fly electronic structure calculations using a semi-empirical Hamiltonian. The simulations represent a collision event between the peptide and an Ar-atom addressing the reactivity at “short” time-scales, i.e. up to 5ps. Simulations were performed for different protonation sites, greatly influencing the reactivity in agreement with what is known from the “mobile proton” model of peptide dissociation. Results are then combined with ESI-MS/MS experiments to determine the fragmentation patterns. Additionally, we used IRMPD spectra to elucidate the structure of these peptides before collisional activation and the structures of some of the CID products. Results are also compared with threshold CID experiments reported in the literature for the non-amidated peptides.Chemical dynamics simulations can provide details on the fragmentation pathways observed. We also show that it is possible to identify the protonation state(s) that are populated in the different steps involved in the fragmentation process. Finally, the chemical dynamics approach is shown to be complementary to the more typical theoretical study of the potential energy surface that becomes more problematic (and sometimes impossible) for systems of increasing complexity.

Ion Mobility-Mass Spectrometry Differentiates Protein Quaternary Structures Formed in Solution and in Electrospray Droplets.

Electrospray ionization coupled to mass spectrometry is a key technology for determining the stoichiometries of multiprotein complexes. Despite highly accurate results for many assemblies, challenging samples can generate signals for artifact protein-protein binding born of the crowding forces present within drying electrospray droplets. Here, for the first time, we study the formation of preferred protein quaternary structures within such rapidly evaporating nanodroplets. We use ion mobility and tandem mass spectrometry to investigate glutamate dehydrogenase dodecamers and serum amyloid P decamers as a function of protein concentration, along with control experiments using carefully chosen protein analogues, to both establish the formation of operative mechanisms and assign the bimodal conformer populations observed. Further, we identify an unprecedented symmetric collision-induced dissociation pathway that we link directly to the quaternary structures of the precursor ions selected.

Studies on the collision-induced dissociation of adipoR agonists after electrospray ionization and their implementation in sports drug testing.

AdipoR agonists are small, orally active molecules capable of mimicking the protein adiponectin, which represents an adipokine with antidiabetic and antiatherogenic effects. Two adiponectin receptors were reported in the literature referred to as adipoR1 and adipoR2. Activation of these receptors stimulates mitochondrial biogenesis and results in an improved oxidative metabolism (via adipoR1) and increased insulin sensitivity (via adipoR2). Hence, adipoR agonists are potentially performance enhancing substances and targets of proactive and preventive anti-doping measures. In this study, two adipoR agonists termed AdipoRon and 112254 as well as two isotopically labeled internal standards (ISTDs) were synthesized in three-step reactions. The products were fully characterized by nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and density functional theory (DFT) computation. Collision-induced dissociation pathways following electrospray ionization were suggested based on the determined elemental compositions of product ions, comparison to product ions derived from labeled analogs (ISTDs), H/D-exchange experiments and the results of DFT calculations. The most abundant product ions were found at m/z 174, tentatively assigned to protonated 1-benzyl-1,2,3,4-tetrahydropyridine for AdipoRon, and m/z 207, suggested as protonated 1-(4-methoxybenzyl)piperazine, for 112254. Notably, the loss of the heterocyclic ring (i.e. piperazine and piperidine, respectively) in a supposedly intramolecular elimination reaction was observed in both cases. A qualitative determination of both AdipoR agonists in human plasma was established and fully validated for doping control purposes. Validation items such as recovery (86-89%), specificity, linearity, lower limit of detection (1 ng/ml), intraday (3-18%) and interday (5-16%) precision as well as ion suppression or enhancement were determined. Based on these findings adipoR agonists can be implemented in sports drug testing procedures.

Understanding dissociation of cyclic dinucleotide ions by electrospray mass spectrometry

Mechanisms of collision induced dissociation (CID) under the conditions of electrospray ionization mass spectrometry (ESI-MS) of cyclic-di-adenosine mono phosphate (c-di-AMP) and cyclic-di-guanosine mono phosphate (c-di-GMP) are described. The CID mass spectrum of doubly protonated ([M+2H]2+) c-di-AMP differs from that of singly protonated ([M+H]+) and the mechanisms of dissociation of these two ionic forms are proposed. CID of singly deprotonated form ([M−H]−) of c-di-AMP was also carried out and its fragmentation mechanism is delineated. Ring-opening step seems to be imperative and foremost prior to subsequent dissociation events, during the fragmentation of both cationic and anionic forms of c-di-AMP. In the case of CID of [M+H]+ of c-di-GMP, the abundance of fragment ions indicate that ring-opening mediated fragmentation may not be a favored pathway, while loss of guanine may be relatively more preferred. Interestingly, fragmentation of [M−H]− of c-di-GMP appears to be very similar to that of c-di-AMP, which involves ring-opening step, suggesting that nitrogen base does not influence CID pathways of [M−H]− species. Understanding such dissociation mechanisms will prove useful for discovery and validation of novel hybrid cyclic dinucleotides and their analogues. Also, such comprehensions will be helpful in distinguishing different isobaric molecules possessing varied molecular structures.

Energy-resolved collision-induced dissociation pathways of model N-linked glycopeptides: implications for capturing glycan connectivity and peptide sequence in a single experiment

Tandem mass spectrometry (MS/MS) of glycopeptides stands among the principal analytical approaches for assessing protein glycosylation in a site-specific manner. The aims of such experiments are often to determine the monosaccharide connectivity of the glycan, the amino acid sequence of the peptide, and the site of glycan attachment. This level of detail is often difficult to achieve using any single ion dissociation method; however, precedent does exist for use of collision-induced dissociation (CID) to establish either the connectivity of the oligosaccharide or the sequence of the polypeptide depending upon the applied collision energy. Unfortunately, the relative energy requirements for glycan and peptide cleavage have not been thoroughly characterized with respect to specific physicochemical characteristics of the precursor ions. This report describes case studies on the energy-resolved CID pathways of model tryptic glycopeptides derived from Erythrina cristagalli lectin and bovine ribonuclease B. While glycopeptide ions having disparate physical and chemical characteristics shared strikingly similar qualitative responses to increasing vibrational energy deposition, the absolute collision energies at which either glycan or peptide fragmentations were accessed varied substantially among the precursor ions examined. Nevertheless, these data suggest that the energy requirements for peptide and glycan cleavage may be somewhat predictable based on characteristics of the precursor ion. The practical usefulness of these observations was demonstrated through implementation of online collision energy modulation such that both glycan and peptide fragmentation were captured in the same spectrum, providing near-exhaustive glycopeptide characterization in a single experiment. Overall, these results highlight the potential to further extend the capabilities of CID in the context of glycoproteomics.

Re-Evaluation of the Proton Affinity of 18-Crown-6 Using Competitive Threshold Collision-Induced Dissociation Techniques

The proton affinity (PA) of 18-crown-6 (18C6) is determined using competitive threshold collision-induced dissociation (TCID) techniques. The PA of 18C6 is derived from four thermochemical cycles involving the relative thresholds for production of the protonated bases, H(+)(B), and protonated crown, H(+)(18C6), from the collision-induced dissociation (CID) of four proton bound heterodimers, (B)H(+)(18C6). The bases examined include glycine (Gly), alanine (Ala), imidazole (Imid), and 4-methylimidazole (4MeImid). In all cases, CID pathways for the loss of intact B and 18C6 are observed in competition. Loss of intact 18C6 is observed as the lowest-energy CID pathway for the (Imid)H(+)(18C6) and (4MeImid)H(+)(18C6) complexes. In contrast, loss of intact Gly and Ala is observed as the lowest-energy CID pathway for the (Gly)H(+)(18C6) and (Ala)H(+)(18C6) complexes, respectively. Excellent agreement between the measured and calculated (B)H(+)-18C6 and (18C6)H(+)-B bond dissociation energies (BDEs) is found with M06 theory, whereas B3LYP theory systematically underestimates these BDEs. On the basis of the relative TCID thresholds for the primary and competitive CID pathways, as well as the literature PAs of the bases, the PA of 18C6 is evaluated. The PA determined here for 18C6 exhibits excellent agreement with M06 and B3LYP theories, and very good agreement with the value reported by Meot-Ner determined using high pressure mass spectrometry (HPMS) techniques, suggesting that the PA of 18C6 reported in the NIST Webbook based on HPMS measurements by Kebarle and co-workers is overestimated.

Novel Fragmentation Pathways of Anionic Adducts of Steroids Formed by Electrospray Anion Attachment Involving Regioselective Attachment, Regiospecific Decompositions, Charge-Induced Pathways, and Ion–Dipole Complex Intermediates

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion](-) adducts of these steroids revealed that fluoride adduct [M + F](-) precursors first lose HF to produce [M - H](-) and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d(4)-pregnenolone, are also discussed.

Interfacing an Ion Mobility Spectrometry Based Explosive Trace Detector to a Triple Quadrupole Mass Spectrometer

Hardware from a commercial-off-the-shelf (COTS) ion mobility spectrometry (IMS) based explosive trace detector (ETD) has been interfaced to an AB/SCIEX API 2000 triple quadrupole mass spectrometer. To interface the COTS IMS based ETD to the API 2000, the faraday plate of the IMS instrument and the curtain plate of the mass spectrometer were removed from their respective systems and replaced by a custom faraday plate, which was fabricated with a hole for passing the ion beam to the mass spectrometer, and a custom interface flange, which was designed to attach the IMS instrument onto the mass spectrometer. Additionally, the mass spectrometer was modified to increase the electric field strength and decrease the pressure in the differentially pumped interface, causing a decrease in the effect of collisional focusing and permitting a mobility spectrum to be measured using the mass spectrometer. The utility of the COTS-ETD/API 2000 configuration for the characterization of the gas phase ion chemistry of COTS-ETD equipment was established by obtaining mass and tandem mass spectra in the continuous ion flow and selected mobility monitoring operating modes and by obtaining mass-selected ion mobility spectra for the explosive standard 2,4,6 trinitrotoluene (TNT). This analysis confirmed that the product ion for TNT is [TNT - H](-), the predominant collision-induced dissociation pathway for [TNT- H](-) is the loss of NO and NO(2), and the reduced mobility value for [TNT - H](-) is 1.54 cm(2)V(-1) s(-1). Moreover, this analysis was attained for sample amounts of 1 ng and with a resolving power of 37. The objective of the research is to advance the operational effectiveness of COTS IMS based ETD equipment by developing a platform that can facilitate the understanding of the ion chemistry intrinsic to the equipment.

Structure characterisation of urinary metabolites of the cannabimimetic JWH-018 using chemically synthesised reference material for the support of LC-MS/MS-based drug testing

As recently reported, the synthetic cannabinoid JWH-018 is the subject of extensive phase I and II metabolic reactions in vivo. Since these studies were based on LC-MS/MS and/or GC-MS identification and characterisation of analytes, the explicit structural assignment of the metabolites was only of preliminary nature, if possible at all. Here, we report the chemical synthesis of five potential in vivo metabolites of JWH-018 derivatives featuring an alkylcarboxy (M1), a terminal alkylhydroxy (M2), a 5-indolehydroxy (M3), an N-dealkylated 5-indolehydroxy (M4) and a 2'-naphthylhydroxy (5) analogue, respectively, and their characterisation by nuclear magnetic resonance spectroscopy. The collision-induced dissociation (CID) patterns of the protonated compounds were studied by high-resolution/high-accuracy tandem mass spectrometry (MS( n )) applying an LTQ Orbitrap with direct infusion and electrospray ionisation of target analytes. An unusual dissociation behaviour including a reversible ion-molecule reaction between a naphthalene cation (m/z 127) and water in the gas phase of the MS was shown to be responsible for nominal neutral losses of 10u in the course of the CID pathway. LC-MS/MS-supported comparison of synthesised reference standards with an authentic urine sample using an API 4000 QTrap mass spectrometer identified the synthetic JWH-018 analogues M1-M4 as true in vivo metabolites, presuming a chromatographic separation of potentially present regioisomeric analogues. Existing doping control methods were expanded and validated according to international guidelines in order to allow for the detection of the carboxy and the alkylhydroxy metabolites, respectively, as urinary markers for the illegal intake of the synthetic cannabinoid JWH-018. Both metabolites were quantified in authentic doping control urine samples that had been suspicious of JWH-018 abuse after routine screening procedures, and a stable isotope-labelled (13)C(8)-(15)N-carboxy metabolite was synthesised for future analytical applications.

Screening for the calstabin‐ryanodine receptor complex stabilizers JTV‐519 and S‐107 in doping control analysis

Recent studies outlined the influence of exercise on the stability of the skeletal muscle calstabin1-ryanodine receptor1-complex, which represents a major Ca(2+) release channel. The progressive modification of the type-1 skeletal muscle ryanodine receptor (RyR1) combined with reduced levels of calstabin1 and phosphodiesterase PDE4D3 resulted in a Ca(2+) leak that has been a suggested cause of muscle damage and impaired exercise capacity. The use of 1,4-benzothiazepine derivatives such as the drug candidates JTV-519 and S-107 enhanced rebinding of calstabin1 to RyR1 and resulted in significantly improved skeletal muscle function and exercise performance in rodents. Due to the fact that the mechanism of RyR1 remodelling under exercise conditions were proven to be similar in mice and humans, a comparable effect of JTV-519 and S-107 on trained athletes is expected, making the compounds relevant for doping controls. After synthesis of JTV-519, S-107, and a putative desmethylated metabolite of S-107, target compounds were characterized using nuclear magnetic resonance spectroscopy and electrospray ionization (ESI)-high-resolution/high-accuracy Orbitrap mass spectrometry. Collision-induced dissociation pathways were suggested based on the determination of elemental compositions of product ions and H/D-exchange experiments. The most diagnostic product ion of JTV-519 was found at m/z 188 (representing the 4-benzyl-1-methyl piperidine residue), and S-107 as well as its desmethylated analog yielded characteristic fragments at m/z 153 and 138 (accounting for 1-methoxy-4-methylsulfanyl-benzene and 4-methoxy-benzenethiol residues, respectively). The analytes were implemented in existing doping control screening procedures based on liquid chromatography, multiple reaction monitoring and simultaneous precursor ion scanning modes using a triple quadrupole mass spectrometer. Validation items such as specificity, recovery (68-92%), lower limit of detection (0.1-0.2 ng/mL), intraday (5.2-18.5%) and interday (8.7-18.8%) precision as well as ion suppression/enhancement effects were determined.

Fragmentation of Isomeric Intrastrand Crosslink Lesions of DNA in an Ion-Trap Mass Spectrometer

The collision-induced dissociation pathways of isomeric cytosine-guanine and cytosine-adenine intrastrand crosslink-containing dinucleoside monophosphates were investigated with the stable isotope-labeled compounds to gain insights into the effects of chemical structure on the fragmentation pathways of these DNA modifications. A Dimroth-like rearrangement, which was reported for protonated 2'-deoxycytidine and involved the switching of the exocyclic N4 with the ring N3 nitrogen atom, was also observed for the cytosine component in the protonated ions of C[5-8]G, C[5-2]A, and C[5-8]A, but not C[5-N(2)]G or C[5-N(6)]A. In these two sets of crosslinks, the C5 of cytosine is covalently bonded with its neighboring purine base via a carbon atom on the aromatic ring and an exocyclic nitrogen atom, respectively. On the contrary, the rearrangement could occur for the deprotonated ions of C[5-N(2)]G, C[5-N(6)]A, and unmodified cytosine, but not C[5-8]G, C[5-2]A, or C[5-8]A. In addition, ammonia could be lost more readily from C[5-N(2)]G and C[5-N(6)]A than from C[5-8]G, C[5-2]A, and C[5-8]A. The results from the present study afforded important guidance for the application of mass spectrometry for the structure elucidation of other intrastrand/interstrand crosslink lesions.

Identification and characterization of supercritical fluid extracts of Rhizoma Chuanxiong by high performance liquid chromatography ion trap mass spectrometry

The main constituents, senkyunolide A, Z-ligustilide, neocnidilide, 3-butylphthalide, and ligustilide dimers, in supercritical CO2 fluid extracts of Rhizoma Chuanxiong, a popular Chinese traditional medicine, have been identified and characterized by high performance liquid chromatography tandem mass spectrometry. Separations were carried out on an Agilent (ECLIPSE XDB) C18 analytical column by gradient elution with 0.25% acetic acid and methanol (containing 0.25% acetic acid). An Agilent 1100 series LC/MSD XCT system was operated under positive ESI and auto MS/MS modes for mass spectrometric analysis. Collision-induced dissociation (CID) fragmentations of these phthalides have been investigated and elucidated. Phthalides have primarily undergone two ESI CID pathways: side-chain cleavage with losses of alkenes and ring-opening with eliminations of H2O followed by losses of CO. Direct neutral loss of CO has not been observed. Sodium adduct ions have demonstrated completely different CID pathways.

How do sphingolipids and lipid rafts relate to pathology?

European Journal of Lipid Science and TechnologyVolume 108, Issue 10 p. 799-801 EditorialFree Access How do sphingolipids and lipid rafts relate to pathology? Gerrit van Meer, Gerrit van Meer Bijvoet Center and Institute of Biomembranes, Utrecht University, Utrecht, The NetherlandsSearch for more papers by this author Gerrit van Meer, Gerrit van Meer Bijvoet Center and Institute of Biomembranes, Utrecht University, Utrecht, The NetherlandsSearch for more papers by this author First published: 09 October 2006 https://doi.org/10.1002/ejlt.200600184Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References 1 S. Hakomori: Glycosphingolipids in cellular interaction, differentiation, and oncogenesis. Annu Rev Biochem. 1981, 50, 733– 764. 2 K. Powell: Lipid raft idea is floated. J Cell Biol. 2006, 172, 166– 167. 3 A. H. Futerman, Y. A. Hannun: The complex life of simple sphingolipids. EMBO Rep. 2004, 5, 777– 782. 4 C. S. Ejsing, T. Moehring, U. Bahr, E. Duchoslav, M. Karas, K. Simons, A. Shevchenko: Collision-induced dissociation pathways of yeast sphingolipids and their molecular profiling in total lipid extracts: a study by quadrupole TOF and linear ion trap-orbitrap mass spectrometry. J Mass Spectrom. 2006, 41, 372– 389. 5 B. Brügger, B. Glass, P. Haberkant, I. Leibrecht, F. T. Wieland, H. G. Krausslich: The HIV lipidome: a raft with an unusual composition. Proc Natl Acad Sci U S A. 2006, 103, 2641– 2646. 6 K. I. Willig, S. O. Rizzoli, V. Westphal, R. Jahn, S. W. Hell: STED microscopy reveals that synaptotagmin remains clustered after synaptic vesicle exocytosis. Nature. 2006, 440, 935– 939. 7 F. Spener, S. D. Kohlwein, G. Schmitz: Lipid droplets and lamellar bodies – from innocent bystanders to prime targets of lipid research for combating human diseases. Eur J Lipid Sci Technol. 2006, 108, 541– 543. 8 F. Spener, R. Zechner, J. Borlak: Is lipotoxicity an oxymoron? Eur J Lipid Sci Technol. 2006, 108, 625– 627. 9 W. J. Griffiths: Why steroidomics in brain? Eur J Lipid Sci Technol. 2006, 108, 707– 708. Citing Literature Volume108, Issue10No. 10 October 2006Pages 799-801 ReferencesRelatedInformation

Collision-Induced Dissociation Pathways of Anabolic Steroids by Electrospray Ionization Tandem Mass Spectrometry

Anabolic steroids are structurally similar compounds, and their product-ion spectra obtained by tandem mass spectrometry under electrospray ionization conditions are quite difficult to interpret because of poly-ring structures and lack of a charge-retaining center in their chemical structures. In the present study, the fragmentation of nine anabolic steroids of interest to the racing industry was investigated by using triple quadrupole mass spectrometer, Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, and a linear ion trap instrument. With the aid of an expert system software (Mass Frontier version 3.0), accurate mass measurements, and multiple stage tandem mass spectrometric (MS(n)) experiments, fragmentation pathways were elucidated for boldenone, methandrostenolone, tetrahydrogestrinone (THG), trenbolone, normethandrolone and mibolerone. Small differences in the chemical structures of the steroids, such as an additional double-bond or a methyl group, result in significantly different fragmentation pathways. The fragmentation pathways proposed in this paper allow interpretation of major product ions of other anabolic steroids reported by other researchers in a recent publication. The proposed fragmentation pathways are helpful for characterization of new steroids. The approach used in this study for elucidation of the fragmentation pathways is helpful in interpretation of complicated product-ion spectra of other compounds, drugs and their metabolites.

Direct analysis of highly oxidised organic aerosol constituents by on-line ion trap mass spectrometry in the negative-ion mode.

On-line ion trap mass spectrometry (ITMS) enables the characterisation of constituents of biogenic secondary organic aerosols in complex organic reaction mixtures. This real-time analysis is achieved by directly introducing the airborne particles into the ion source of the mass spectrometer. Negative-ion chemical ionisation at atmospheric pressure (APCI(-)) was used as the ionisation method of choice. The aerosols were generated from the gas-phase ozonolysis of two C10H16-terpenes (alpha-pinene and limonene), and investigated by performing on-line APCI(-)-ITMS(n). Highly oxidised compounds were tentatively identified as important particle-phase products. Based on recent investigations of low-energy collision-induced dissociation pathways of a wide range of deprotonated multifunctional carboxylic acid species derived from monoterpene precursors (Warscheid B, Hoffmann T. Rapid Commun. Mass Spectrom. 2001; 15: 2259), the formation of structurally different C10H16O5 and C10H16O6 species, such as acidic esters from alpha-pinene and aldo-hydroxycarboxylic acids from limonene, is proposed.

Site-specific lithium ion attachment directs low-energy dissociation pathways of dinucleotides in the gas phase. Application to nucleic acid sequencing by mass spectrometry

Fourier transform ion cyclotron resonance mass spectroscopy has been used to examine the low-energy collision-induced dissociation pathways of lithiated dinucleotides. Collisional activation using continuous off-resonance excitation permits observation of energetically-favorable dissociation pathways. Dissociation products were examined under multiple collision conditions for center of mass collision energies from 0 eV to the minimum energy required to bring about complete dissociation of the reactant ion (7.0 eV). The lithiated molecular ions dissociate to yield several characteristic products. The major fragmentation pathways observed in most systems are directed by localization of charge on the phosphate moiety leading to cleavage of the 3′-phosphate diester linkage to produce the 3′-sequence ion. In some systems, loss of the 5′-terminus base from the lithiated parent ion is also observed. Exceptions are observed only in systems where guanine is the 3′-terminus base. In these systems, the major products observed are the ion resulting from loss of the neutral 3′-terminus base along with its dehydrated decedent ion, the 5′-sequence ion and the ion resulting from loss of water from the 5′-sequence ion. Reaction mechanisms which account for the observed products are proposed. The present results suggest that collisional activation of lithiated oligonucleotides may provide useful sequence information.

Qualitative and Quantitative Analyses of Phenolic Compounds by High-performance Liquid Chromatography and Detection with Atmospheric Pressure Chemical Ionization Mass Spectrometry

High-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in the negative-ion mode has been succesfully used for qualitative and quantitative determination of fifteen phenolic compounds found in olive mill wastewater. APCI gives information about both the molecular weight of these molecules and about their structure, showing consistent collision-induced dissociation pathways, which have been elucidated to give detailed information about the structure of the fragments. Quantitative analysis, using p-bromophenol as an internal standard, was carried out using calibration graphs for injections in the 0.01–1000 ng range, working both in scanning and selected-ion monitoring data aquisition modes, resulting in correlation coefficients higher than 0.98 for all compounds.